Knives for fiber tow-cutting apparatus

ABSTRACT

In knives for the fiber tow-cutting for manufacturing staples by cutting synthetic tows, the improvement comprising I. MAKING THE BLADE BODY OF SUCH KNIVES OF A STEEL MATERIAL HAVING THE FOLLOWING COMPOSITION: Content of C0.08 - 1.10% by weightContent of Si0.15 - 0.80% by weightContent of Cr0.40 - 1.80% by weight Total content of Mn, P and S0 - 1.75% by weightContent of metallicimpurities otherthan Fe and theabove components0 - 5.00% by weightContent of Eeremainder of a total of 100% by weight; and II. PROVIDING ONLY ON ONE SIDE OF SUCH KNIVES A METALLIC COATING LAYER A THICKNESS RANGING FROM 2 MICRONS TO 50 MICRONS AND A Vickers hardness of above 700.

United States Patent 1 Kinoshita et al.

[ 1 May 15, 1973 KNIVES FOR FIBER TOW-CUTTING APPARATUS [75]' Inventors:Saijiro Kinoshita; Kats'unobu Shinmura, both of Matsuyama-shi,Ehime-ken, Japan [73] Assignee: Teijin Limited, Osaka, Japan [22] Filed:July 7, 1971 [21] Appl. No.: 160,293

[30] Foreign Application Priority Data Aug. 26, 1970 Japan 45/748123[52] US. Cl.' .l..83/663, 83/355, 83/701 [51] Int. Cl. ..B26d 1/28 [58]Field of Search ..83/675, 673, 403, 83/592, 355, 663, 70]; 29/95 D, 95R; 76/161 A [56] References Cited UNITED STATES PATENTS 2,747,663 5/1956Cook 2,792,887 5/1957 Midde|hof.. 3,387,521 6/1968 Okamoto ..83/355above components Primary ExaminerFrank T. Yost A ttorney-Sherman &Shalloway [57] ABSTRACT In knives for the fiber tow-cutting formanufacturing staples by cutting synthetic tows, the improvementcomprising i. making the blade body of such knives of a steel materialhaving the following composition:

Content ofC 0,08 1.10% by weight Content of Si 0.15 0.80% by weightContent of Cr 0.40 1.30% by weight Total content of Mn, P and S 0 1.75%by weight Content of metallic impurities other than Fe and the 0 5.00%by weight remainder of a total of I00% by weight; and

Content of Be ii. providing only on one side of such knives a metalliccoating layer a thickness ranging from 2 microns to 50 microns and aVickers hardness of above 700.

9 Claims, 5 Drawing Figures I PATENTED HAY 1 $1973 l KNIVES FOR FIBERTOW-CUTTING APPARATUS This invention relates to improvements in knivesused for cutters which are employed in the manufacture of staple fibersby cutting synthetic tows and, in particular, knives used for cuttersheretofore known as a so-called Gru-Gru cutter. The use of the improvedknives in the invention not only prevents synthetic tows from beingmiscut but also greatly reduces occurrence of fused end fibers incutting, accordingly sharpness of the cutter knives can be maintainedstably for a long time, and marked improvements in the operatingefficiency and productivity are made possible. The term fused end fibersrefers to a state wherein at least two adjacent monofilaments are inintimate cohesion at the cut plane.

More specifically, the invention relates to knives for a cutter in usedin manufacturing staple fibers by cutting a synthetic tow, and theknives are characterized by as follows:

i. The blade of the knives is made of steel having the followingcomposition:

Content ofC 0.08 1.10 by weight,

preferably 0.45 1.10% by weight, still more preferably 0.80 1.10% byweight, particularly 0.95 1.10% by weight (SUJ designated in .115)Content of Si 0.15 0.80% by weight,

preferably 0.15 0.70% by weight 0.40- 1.80% by weight, preferably 0.501.60% by weight, still more preferably 0.90 1.60 by weight 1.75% byweight, preferably Content of Cr Content of Fe and the ii. A layer ofmetallic coating is provided only on one side of the knife, such layerhaving a thickness ranging from 2 to 50 microns, and preferably 2 25microns, and a Vickers hardness of above 700.

The conventional knife material in the Gru-Gru cutter has beendisclosed, for example, in US. Pat. No. 2,792,887. The knives used inthis type of cutter have previously been made of steel materials such ashigh speed steel, stainless steel or carbon tool steel and have beengiven a suitable heat treatment to the edges thereof. These knives havebeen used mounted on the knife-head of the Gru-Gru cutter.

However, when staple fibers have been manufactured by cutting synthetictows as, for example, polyester type, polyamide type or polyolefin type,using the Gru-Gru cutter equipped with knives made of the steelmaterials such as beforementioned, the edges of the knives lose theirsharpness in a very short time in continuous use, for example, as shortas about 20 minutes. Now, if those dulled knives are forced to be used,either fused end fibers or imperfect cuttings finally make it impossibleto continue the cutting operation.

Therefor, it becomes necessary to perform the operation of exchangingthe knives at very short intervals of operation. There is not only thedisadvantage from operative standpoints that the troublesome exchangingoperation must be performed frequently and that labor is required forthis purpose but also the result that the low productivity isinevitable.

Further, the edges of the knives are susceptible to chipping during thecutting of a tow. Therefore, these chips may be mixed in the staplefibers and cause problems in the subsequent treatment steps of thespinning process. Still further the nicked edges entail problems such asmiscutting or fusing of the tow which occurs in the case of the use ofdulled edged knives as hereinbefore described.

Knives for fiber tow-cutting apparatus have been studied in an attemptto overcome these drawbacks of the prior art. As a result, it has beenhave found that the knives for the Gru-Gru cutter whose properties havebeen markedly improved can be obtained by making the blade body of theknives with the steel material of the hereinbefore describedcomposition, i.e., one belonging to the category of bearing steels whichhave been heretofore used in an area different from that of cutlery suchas knives of the Gru-Gru" cutter, and by providing the blade body, onone side only, with a layer of metallic coating, and preferable chromiumplating layer ofa thickness between 2 microns and 50 microns and aVickers hardness of about 700, preferably above 800.

An object of the present invention therefore is to overcome thedrawbacks in the conventional knives for the Gru-Gru cutter and toprovide knives for the Gru-Gru cutter whose excellent cutting abilitycan be stably maintained for an especially prolonged period of timewithout miscutting tow or fused end fibers, thereby making it possibleto demonstrate a pronounced improvement in the working efficiency andproductive capability in the manufacture of staple fibers.

Other objects and advantages of the invention will become apparent tothose skilled in the art from the following description.

It has been known to apply chromium plating to the entire blade portionof knives in the case of paring knives and other knives for home use toimpart rust resistance and surface luster and smoothness to the knives,or to apply chromium plating to such tools for machining metals asdrills, cutters, taps, reamers and tools to reduce the surfacecoefficient of friction of the edge portion and prevent adhesion of thetool to other metals.

The present invention departs from the conventional conception of usingcutlery steel as the steel material of knives for the Gru-Gru cutterwhich is used specifically for cutting synthetic tows, and instead usesthe steel material which has hitherto been used principally for bearingpurposes in view of its suitability therefor. The knives according tothe invention are made of bearing steel and are provided on one sideonly with a thin layer of a metallic coating preferably a chromiumplating layer of less than 50 microns in thickness and preferably a thinlayer within specified limits, and of Vickers hardness of above 700.Thus, in carrying out cutting of synthetic tows, the distal portion ofthe metallic chromium coating layer exposed at the knife edgeparticipates directly in the cutting operation. Therefore, since theblade with a major portion of the knife, is made of the steel materialas hereinabove described and this is covered only on.one side with theaforesaid metallic coating, the dulling of the knives in an extremelyshort period of time carrying out cutting of synthetic tows has not onlybeen ingeniously avoided but also such other drawbacks as the entry intothe staple fiber stock of chips resulting from the nicking of the edgehas been conveniently overcome, and the occurrence of miscuts and fusingof the tows during their cutting have also entirely been overcome. Thus,the invention has succeeded in achieving remarkable improvements inincreasing the life of knives as well as working and productiveefficiency of the operation of cutting the synthetic tow. Thissurprising improved effect will be readily appreciated in connectionwith the results of the hereinafter given examples and comparative data.

Next, for easier understanding of the invention, the improved knives forthe Gru-Gru cutter will be described with reference to the accompanyingdrawings in which; FIG. 1 is a plan view of one embodiment of the knivesof the present invention, a plurality of which are exchangeably mountedand secured to the knifehead ofa Gru-Gru cutter; FIG. 2 is a enlargedcrosssectional view taken along line AA of FIG. 1; FIG. 2' is across-sectional view of a conventional knife similar to that of FIG. 2;FIG. 3 is a cross-sectional view similar to that of FIG. 2 illustratingthat of another embodiment of the invention; and FIG. 4 is a similarenlarged cross-sectional view partly cut away illustrating the edgeportion of the knife of the invention.

Referring now to FIG. 1, an arm 4 by which the knife is mounted to theknife-head is provided with a mounting hole 5. The knife portion extendsfrom the arm 4 in angular relationship to the planar axis of the arm.

The blade body 1 extended usually is provided with a face 1' at the edgeportion of the blade body just before arriving at the knife edge, and aface 2' of the terminal portion of the coating of the layer 2 ofmetallic coating (see FIG. 2) appears at the terminal portion of theedge. This forms an extremity 3 of the edge. FIG. 2 shows the edge bymeans of a cross-sectional view taken along line A-A of FIG. 1. In FIGS.1 and 2 the blade body 1 inclusive of the face 1 is made ofa steelmaterial having the composition given in (i), beforementioned. The bladebody 1 is provided only on its one side with a metallic coating layer ofa thickness ranging from 2 microns to 50 microns, preferably 2 25microns, especially 5 25 microns, and ofa Vickers hardness of above 700,preferably above 800. The terminal portion of this metallic coatinglayer appears beyond the terminal edge portion of the blade body 1 toform the edge of the knife. Therefore, in the knife of the invention thematerial of which this metallic coating layer is made plays a directrole in determining the cutting life of the knife when used in theoperation of cutting synthetic tows.

On the other hand, in the case of the conventional knife, as shown inFIG. 2', the material such, for example. as high speed steel of whichthe blade body 1 is made extends to the terminal portion of the edge.Therefore, since the blade body and the terminal portion ofthe edge aremade of the same material, the material of which the blade body is madeplays a direct role in determining the tow cutting ability of the knife.

In the knife ofthe invention, as materials for forming the aforesaidmetallic coating layer, the metallic materials such, for example, aschromium, tungsten or tungsten carbides can be used, and chromium ismost preferable.

The methods of forming the metallic coating layer are already known. Anyof'the various methods by which the blade body and the metallic coatinglayer can be firmly bonded can be employed. As to forming methods theelectroplating method, the flame plating method and the soldering orbonding method can be mentioned.

FIG. 3 illustrates a modification of a knife similar to that shown inFIG. 2. This embodiment is provided with a face 1" in addition to theface 1. The edge angle a of the knives according to the invention ispreferably 5- 40, especially 10- 30. The edge angle a, as here used,denotes, as shown in FIGS. 2 and 3, an angle made in the A-A linesection, at right angles to the axis of the knife, by the face 1'extending directly to the tip 3 of the blade and a tangent to thecurvilinear surface of the metallic coating layer.

In the invention the surface of the metallic coating layer shouldpreferably have a Vickers hardness of above 800, and this shouldpreferably be at least 50 higher in the Vickers hardness than thesurface of the steel material of which the blade body is made.

FIG. 4 is a partly cutaway cross-sectional view of the knife edgeterminal portion. In FIG. 4, owing to the presence of such a differencein Vickers hardness as indicated above, the face 1', though originallyof the form shown by the dotted line in the figure, abrades at all timesahead of the face 2 of the terminal portion of the coating formed at theknife edge. As a result, the face 1' becomes as shown by 1 in the figureand, as a consequence, promotes the maintenance of the face 2',including the knife edge extremity 3, continually in a sharp state. Inthe conventional knife such as shown in FIG. 2 the knife edge terminalportion, including the knife edge extremity 3, abrades at the same rateas the blade body material, with the consequence that the edge becomesdull.

In the case of the knives for the Gru-Gru cutter of the presentinvention, their cutting ability is thus maintained for an exceptionallyprolonged period of time. The following test is carried out fordetermining this improved durability.

DURABILITY IMPROVEMENT RATE TEST.

A Gru-Gru cutter whose knife-head is mounted with the knives to betested is used, and the cutting of synthetic tows is carried out at acutting speed of I00 meters per minute.

After the cutting operation has been started, sampling is carried outevery S-minutes, taking 10 grams of the cut staple fibers in eachsampling. From the obtained samples one gram thereof is taken at randomand from the obtained 1 gram of sample I milligram sample is furthertaken at random. For example, in the case of 1.4 denier nylon filamenttow about 120 I ends of monofilaments are contained in the final sample.

The foregoing sample which has been taken at random, as hereinabovedescribed, is observed under a microscope (magnification: I40 times) andthe time (min.)at which of the number of filaments contained in thefinal sample the cut ends of 20 percent become fused is determined andthis time is designated the durability time X.

Separately, standard knives made of a high speed steel (JIS G4403SKTT4B) of the following composition:

Component Weight 71 0.70 0.85 Si not more than 0.35 Mn do. 0.60 P do.0.03 S do. 0.03 Cr 3.50 4.50 W 18.00 20.00 V 1.00 1.50 Co 1400 16.00Impurities not more than 0.50

(impurities must not contain more than 0.25 "/1 Cu and 0.25 Ni) Feremainder of 100 weight '70,

Durability improvement rate [(X Y)/Y] X 100 v The following examples aregiven for further illustration of the invention.

EXAMPLES I 111,CONTROL AND COMPARISONS I VIII Several classes of knivesfor Gru-Gru cutter use were made, some of which satisfied and some ofwhich did not satisfy the steel composition of the knife blade body andthe metallic coating layer conditions of the invention. The test for thedurability improvement was carried outwith the results shown in Table l.The steel compositions of the blade body materials indicated in Table 1under the experiment numbers are as follows:

Blade Composition of Steel Material (wt.

Body Impurimaterial C Si Cr Mn+P+S ties Fe No. l 0.900.55 1.55 0.88 0.60remainder No. 2 000.25 1.40 0.35 0.45 do No. 3 0.850.60 1.60 1.45 0.52do No.4 0.850.20 0.35 0.30 1.80 do No. 5 1.00030 4.55 0.65 1.50 do No.60.300135 13.00 0.80 0.50 do Note.

No. 1 ASTM 52100 Model 1 No 2 SU] 2(J1S) No.3 ASTM 52100 Model 2 No.4SKD 42 (.115) No.5 SKD 12 (113) No. 6 SUS 53(J1S) The test was carriedout using a tow of total denier of 500,000 consisting of polyestersynthetic fibers (drawn) of monofilament denier of 1.4. The knives hadan edge angle of 27.

TABLE 1 Experi- Blade Metallic Coating Layer Durability iment BodyThickness Vickers Improve- No. Material Metal (micron) Hardness ment Ex.1 No. 1 Cr 800 1400 Ex. 11 No. 2 Cr 5 820 2900 Ex. 111 No.3 Cr 15 7901300 Control high speed steel 0 for use in standard knives Comparison 11No.5 60 111 .No. 6 40 1V No. 2 Cr 1.5 820 2000 V No. 2 Cr 20 650 1000 VINo. 2 Cr 55 820 500 VII No. 2 10 820 150 *Both sides of knife wereapplied a chromium plating.

EXAMPLE 1V AND COMPARISONS VIII 1X Blade body'materials of the followingtwo classes of compositions were used and knives of identical shape weremade in each case. The durability improvement test was then carried outin accordance with the hereinbe'fo r'e described method to determinetheir respective durability times X. The average durability time of the100 knives, the durability improvement rate and the number of knives inwhich damage of the knife edges were noted in the case of each of theseclasses of knives are shown in Table 2. The tow used in this test wasthe same as that used in Example 1,

No.8 SKH 2 (.118)

EXAMPLE V AND COMPARISON X Blade body materials of the following twoclasses of compositions were used, and 100 knives each of the same shapewere made. These knives were tested as in Example IV with the resultsshown in Table 3, below. 7 1. 8 2

Blade Composition of Steel Materials (wt. 7:) Body Impuri- Material C SiCr Mn+P+S ties Fe No. 9 0.45015 0.45 0.86 0.97 remainder No. 10 0140.4012.50 0.75 0.55 do.

The tow used was of total denier 500,000 consisting of polyestersynthetic fibers (drawn) of monofilament denier of 1.4.

TABLE 3 Metallic Coating Layer (plated on one side only) Average KnifeDur- Edge Blade ability Damaged Exper. Body Thickness Vickers Time (per100 No. Material (micron Hardness (min.) knives) metal Example V No. 9Cr 5 830 240 Comparison X No. 10Cr 5 830. 60

The results of the durability improvement tests of the foregoingExamples IV and V and Comparisons V111, IX and X are shown in Table 4,below.

TABLE4 Experiment Durability Improvement No. Example IV 1700 do. V 1 100Comparison Vlll 350 do. lX 100 do. X 200 We claim:

1. In knives for fiber tow-cutting apparatus for manufacturing staplesby cutting synthetic tows, the improvement wherein i. the blade body ofthe knife is formed ofa steel material having the following composition:

Content of C 0.08 1.10 7: by weight Content of Si 0.15 8.80 by weightContent of Cr 0.40 1.80 by weight Total content of Mn, 1.75 '74 byweight P and S Content of metallic impurities other than Fe and theabove components Content of Fe 0 5.00 by weight remainder of a total of100 7! by weight; and

ii. one side of said knife is provided with a metallic coating layer ofa thickness ranging from 2 microns to 50 microns and of Vickers hardnessof above 700.

2. The knife of claim 1 wherein i. the composition of said steelmaterial is as follows:

Content of C Content'of Si Content of Cr Total content of Mn,

P and S Content of metallic impurities other than Fe and the abovecomponents 0.45 1.10 by weight 0.15 0.70 by weight 0.50 1.60 by weight 01.21 7t by weight 0 2.20 7: by weight remainder of a total of 100 byweight, and

Content of Fe of the surface of the coating layer on one side of saidblade is at least 50 higher than that of the surface of the said bladeportion made of steel material.

I 6. The knife of claim 1 wherein i. the composition of said steelmaterial is as follows:

Content of C 0.80 1.10 by weight Content of Si 0.15 0.70 by weightContent of Cr 0.90 1.60 by weight Total content of Mn, 0 1.21 by weightP and S Content of metallic O 0.50 by weight impurities other than Feand the above components Content of Fe remainder of a total of 100 byweight; and

ii. a metallic coating layer of chromium of thickness of 5 25 micronsand Vickers hardness of above 700 is provided only on one side of saidknife, and the edge angle a of said knife is 10 30.

7. The knife of claim 2 wherein the edge angle a of said knife is 5044071405 40.

8. The knife of claim 2 wherein the metal forming said coating layer onone side of said blade is chromium.

9. The knife of claim 2 wherein the Vickers hardness of the surface ofthe coating layer on one side of said blade is at least 50 higher thanthat of the surface of the said blade portion made of steel material.

2. The knife of claim 1 wherein i. the composition of said steelmaterial is as follows: Content of C 0.45 - 1.10 % by weight Content ofSi 0.15 - 0.70 % by weight Content of Cr 0.50 - 1.60 % by weight Totalcontent of Mn, 0 - 1.21 % by weight P and S Content of metallic impuri-0 -2.20 % by weight ties other than Fe and the above components ContEntof Fe remainder of a total of 100 % by weight, and ii. the thickness ofsaid metallic coating layer is 2 - 25 microns.
 3. The knife of claim 1wherein the edge angle Alpha of said knife is 5*- 40*.
 4. The knife ofclaim 1 wherein the metal forming said coating layer on one side of saidblade is chromium.
 5. The knife of claim 1 wherein the Vickers hardnessof the surface of the coating layer on one side of said blade is atleast 50 higher than that of the surface of the said blade portion madeof steel material.
 6. The knife of claim 1 wherein i. the composition ofsaid steel material is as follows: Content of C 0.80 - 1.10 % by weightContent of Si 0.15 - 0.70 % by weight Content of Cr 0.90 - 1.60 % byweight Total content of Mn, 0 - 1.21 % by weight P and S Content ofmetallic 0 - 0.50 % by weight impurities other than Fe and the abovecom-ponents Content of Fe remainder of a total of 100 % by weight; andii. a metallic coating layer of chromium of thickness of 5 - 25 micronsand Vickers hardness of above 700 is provided only on one side of saidknife, and the edge angle Alpha of said knife is 10* - 30*.
 7. The knifeof claim 2 wherein the edge angle Alpha of said knife is 5* - 04407140540*.
 8. The knife of claim 2 wherein the metal forming said coatinglayer on one side of said blade is chromium.
 9. The knife of claim 2wherein the Vickers hardness of the surface of the coating layer on oneside of said blade is at least 50 higher than that of the surface of thesaid blade portion made of steel material.